Method of transmitting data using repetition coding

ABSTRACT

A method of transmitting data in a wireless communication system is provided. The method includes generating duplicate data by using repetition coding, the duplicate data being the same as original data, shifting the phase of the duplicate data, and transmitting the original data and the phase-shifted duplicate data. The duplicate data is mapped to a modulation symbol having a different size or phase as that of the original data, thus to reduce the PAPR unlike the general repetition coding.

This application is a continuation reissue of U.S. application Ser. No.14/337,931 filed Jul. 22, 2014, which is a continuation reissue of U.S.application Ser. No. 14/106,602 filed Dec. 13, 2013, which is a reissueof, and claims the benefit of U.S. Pat. No. 8,391,380, issued on Mar. 5,2013, which is a 35 U.S.C. § 371 National Stage entry of InternationalApplication No. PCT/KR2008/005164, filed on Sep. 3, 2008, and claimspriority to the benefits of Korean Application No. 10-2007-0088830,filed on Sep. 3, 2007 and Korean Application No. 10-2007-0099954, filedon Oct. 4, 2007 each of which is are hereby incorporated by reference inits their entirety as if fully set forth herein.

TECHNICAL FIELD

The present invention relates to wireless communication and, moreparticularly, to a method of transmitting data using repetition coding.

BACKGROUND ART

Research on a 4G (4th Generation) mobile communication system, anext-generation communication system, is actively ongoing to provideservices with various QoS (Quality of Service) with a transfer rate ofabout 10 Mbps to users. The 4G mobile communication system is beingstandardized to aim at cooperatively operating a wired communicationnetwork and a wireless communication network and providing integratedservices, beyond simple wireless communication services such as mobilecommunication systems of a previous generation.

As a large capacity communication system, which may process and transmitvarious information such as images, radio data, or the like, beyondvoice-centered services, is requested, development of a techniqueallowing transmission of large capacity data similar to the capacity ofthe wired communication network to the wireless communication network ison demand.

Thus, a proper channel coding method that can improve a systemperformance by minimizing a loss of information and increasing theefficiency of system transmission is recognized and admitted as anessential factor. In general, in order to reduce information loss, thereliability of a system is increased by using various channel codingsdepending on the properties of channels, one of which is a repetitioncoding. In the repetition coding, original data to be transmitted isrepeated to generate a plurality of same data as the original data.Because the duplicate data, which is the same as the original data, aregenerated and transmitted together with the original data, theprobability of a transmission error can be reduced.

In general, in an OFDM (Orthogonal Frequency Division Multiplexing)system, spectrums of sub-channels overlap with each other whilemaintaining cross-orthogonality, having good spectrum efficiency, andbecause OFDM modulation/demodulation is implemented by IFFT (InverseFast Fourier Transform) and FFT (Fast Fourier Transform), amodulating/demodulating unit can be effectively implemented digitallyand resistant to a frequency selective fading or a narrowbandinterference.

Despite such advantages, the OFDM system is disadvantageous in that ithas a high peak-to-average power ratio (PAPR). The OFDM transmits databy using many carriers, so a final OFDM signal has the size of amplitudetantamount to the sum of amplitude sizes of the respective carriers,having a severe change width of amplitude, and if the phases of thecarriers correspond, a quite large value can be obtained. In particular,in case of using the repetition coding in the OFDM system, the same datais repeatedly transmitted, and for uplink, a resource allocation regiondoes not have a square shape, making it difficult to lower the PAPR andpossibly degrading the performance of the system.

Thus, in order to data by using repetition coding, a method for loweringthe PAPR is required.

DISCLOSURE OF INVENTION Technical Problem

An object of the present invention is to provide a method oftransmitting data using repetition coding capable of reducing a PAPR bydividing data obtained through repetition coding and mapping the divideddata to different modulation symbols.

Technical Solution

According to an embodiment of the invention, a method of transmittingdata in a wireless communication system is provided. The method includesgenerating duplicate data by using repetition coding, the duplicate databeing the same as original data, shifting the phase of the duplicatedata, and transmitting the original data and the phase-shifted duplicatedata.

According to another embodiment of the invention, a method oftransmitting data in a wireless communication system is provided. Themethod includes generating duplicate data which is the same as originaldata by using repetition coding, changing the size and the phase of theduplicate data, and transmitting the original data and the duplicatedata with the changed size and phase.

According to still another embodiment of the invention, a datatransmitter is provided. The data transmitter includes a data processingunit to perform repetition coding for original data to generateduplicate data, a data changing unit to shift the phase of the duplicatedata, and a subcarrier allocating unit to map the original data and thephase-shifted duplicate data to a subcarrier.

Advantageous Effects

In the present invention, because the original data, the result ofrepeated coding, and duplicate data are discriminated and the duplicatedata is mapped to a modulation symbol having a different size or phaseas that of the original data and transmitted, to thus reducing the PAPRunlike the general repetition coding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows an example of a frame structure.

FIG. 3 is a schematic block diagram of a transmitter according to anembodiment of the present invention.

FIG. 4 shows a method of repetition coding according to anotherembodiment of the present invention.

FIG. 5 shows a method of repetition coding according to an embodiment ofthe present invention.

FIG. 6 is a graph comparatively showing PAPRs in case of using therepetition coding according to Table 1 to Table 4.

MODE FOR THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings so thatthis disclosure can be through and complete, and will fully convey theconcept of the invention to those skilled in the art.

FIG. 1 shows a wireless communication system. The wireless communicationsystem can be widely deployed to provide a variety of communicationservices, such as voices, packet data, etc.

Referring to FIG. 1, the wireless communication system includes a basestation (BS) 20 and at least one user equipment (UE) 10. The BS 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as a node-B, a base transceiversystem (BTS), an access point, etc. There are one or more cells withinthe coverage of the BS 20. The UE 10 may be fixed or mobile, and may bereferred to as another terminology, such as a mobile station (MS), auser terminal (UT), a subscriber station (SS), a wireless device, etc.

A downlink represents a communication link from the BS 20 to the UE 10,and an uplink represents a communication link from the UE 10 to the BS20. In the downlink, a transmitter may be a part of the BS 20, and areceiver may be a part of the UE 10. In the uplink, the transmitter maybe a part of the UE 10, and the receiver may be a part of the BS 20.

Downlink and uplink transmissions can be made using different multipleaccess schemes. For example, orthogonal frequency division multipleaccess (OFDMA) may be used for downlink transmission, and singlecarrier-frequency division multiple access (SC-FDMA) may be used foruplink transmission.

There is no restriction on the multiple access scheme used in thewireless communication system. The multiple access scheme may be basedon code division multiple access (CDMA), time division multiple access(TDMA), frequency division multiple access (FDMA), single-carrier FDMA(SC-FDMA), orthogonal frequency division multiple access (OFDMA), orother well-known modulation schemes. In these modulation schemes,signals received from multiple users are demodulated to increasecapacity of the communication system.

FIG. 2 shows an example of a frame structure. The frame refers to a datasequence during a fixed time period used by physical specifications, andit may be an OFDMA frame.

With reference to FIG. 2, the frame includes a downlink frame and anuplink frame. Time division duplex (TDD) refers to a method in whichuplink and downlink transmissions take place in the same frequencybandwidth but occur at each different time. The downlink frametemporally goes ahead of the uplink frame. The downlink frame includes apreamble, a frame control header (FCH), a DL (Downlink)-MAP, a UL(Uplink)-MAP, a downlink burst region. The uplink frame includes anuplink burst region.

A guard time for discriminating the uplink frame and the downlink frameis inserted to a middle portion of the frame (i.e., between the downlinkframe and the uplink frame), and to a final portion (after the uplinkframe). A transmit/receive gap (TTG) refers to a gap between thedownlink burst and the subsequent uplink burst. A receive/transmittransition gap (RTG) refers to a gap between the uplink burst and asubsequent downlink burst.

The preamble is used for initial synchronization, cell search, frequencyoffset, and channel estimation between a base station and a mobilestation. The FCH includes the length of a DL-MAP message and repetitioncoding information used for the DL-MAP message. The DL-MAP is a regionon which the DL-MAP message is transmitted. The DL-MAP message definesan access of a downlink channel. The DL-MAP message includes aconfiguration change count of a DCD (Downlink Channel Descriptor) and abase station ID (Identifier).

The DCD describes a downlink burst profile applied to a current map. Thedownlink burst profile refers to characteristics of a downlink physicalchannel, and the DCD is periodically transmitted by the base station viaa DCD message. The UL-MAP is a region on which a UL-MAP message istransmitted. The UL-MAP message defines an access of an uplink channel.The UL-MAP message includes a configuration change count of a UCD(Uplink Channel Descriptor) and a valid start time of uplink allocationdefined by the UL-MAP.

The UCD describes an uplink burst profile. The uplink burst profilerefers to characteristics of an uplink physical channel, and the UCD isperiodically transmitted by the base station via a UCD message.

A portion of the uplink frame includes a fast feedback region. The fastfeedback region is allocated for a faster uplink transmission thangeneral uplink data, and a CQI, ACK/NACK signal, or the like, may beincluded in the fast feedback region. The fast feedback region may bepositioned anywhere in the link frame and not necessarily limited to theillustrated position or size.

Hereinafter, a slot is a minimum possible data allocation unit anddefined as time and a subchannel. In the uplink, subcarrier may includea plurality of tiles. The subcarrier may include six tiles and in theuplink, one burst may include three OFDM symbols and one subcarrier.

In a PUSC (Partial Usage of Subchannels) permutation, each tile mayinclude four contiguous subcarriers on three OFDM symbols. In anoptional PUSC permutation, each time may include three contiguoussubcarriers on three OFDM symbols. The tiles included in the subcarriersare distributed to every band so as to be disposed.

A bin includes nine contiguous subcarriers on an OFDM symbol. A bandrefers to a group of four rows of the bin, and AMC (Adaptive Modulationand Coding) subcarrier includes six contiguous bins in the same band.

The FCH including information regarding repetition coding is merely oneexample of being applied to the system having the frame structure asshown in FIG. 2. Namely, the FCH may be included in a different channelin a different frame structure without being limited to such a framestructure as shown in FIG. 2. Hereinafter, an apparatus and method fortransmitting data by using repetition coding according to the presentinvention will be described.

FIG. 3 is a schematic block diagram of a transmitter according to anembodiment of the present invention.

With reference to FIG. 3, the transmitter 100 includes a data processingunit 110, a data changing unit 120, and a subcarrier allocating unit130. The transmitter 100 may be a part of a base station (BS). The BSrefers to a fixed station communicating with a terminal, and may becalled a node-B, a base transceiver system (BTS), an access point (AP),or other terms.

The data processing unit 110 repeatedly codes inputted information bitsto generate duplicate information bits which are the same as informationbits, and maps the information bits and the duplicate information bitsto data symbols expressing positions on a signal constellation.Hereinafter, the symbol level data generated by mapping the informationbits is called original data and the symbol level data generated bymapping the duplicate information bits is called duplicate data.

The number of duplicate data differs according to the determined numberof times of repetition in a system. The information about the number oftimes of repetition coding is signaled by the transmitter to a receivervia the FCH in the system having such a frame structure as shown in FIG.2. There is no limitation in the number of times of repetition, and thenumber of times of repetition may be set two times, four times or sixtimes depending on systems.

The data processing unit 110 discriminates the original data and theduplicate data and sends the original data to the subcarrier allocatingunit 130 and the duplicate data to the data changing unit 120.

The data changing unit 120 changes the phase or the size or the phaseand size of the duplicate data and transmits the same to the subcarrierallocating unit 130. Hereinafter, the original data is S_(N) and theduplicate data having a phase which has been shifted by θ by the datachanging unit 120 and has a size of k times is ke^(jθ)S_(N). θ is aphase difference of the original data and the duplicate data withrespect to the same information bits, and ‘k’ is a ratio of the size ofthe duplicate data to the original data. Let e^(jθ) be α forconvenience's sake. The duplicate data that has passed through the datachanging unit 120 would be kαS_(N). Here, if ‘k’ is 1, it means thatonly the phase of the original data has been shifted, and if ‘α’ is 1,it means that only the size of the original data has been changed.Because ‘k’ and ‘α’ are variables, if the two variables changeindependently, the duplicate data may be data obtained as both the phaseand the size of the original data have been all changed.

The data changing unit 120 may change only the size of the original datato generate duplicate data, or change only the phase of the originaldata to generate duplicate data, or change both the size and the phaseof the original data to generate duplicate data. A PAPR (Peak-to-AveragePower Ratio) can be reduced by differentiating the phase or the size ofthe original data and the duplicate data and transmitting data.

The subcarrier allocating unit 130 appropriately allocates (or maps)inputted original data and duplicate data to subcarriers and multiplesthem according to users. The subcarrier allocating unit 130 may usevarious multiplexing schemes such as OFDM as well as SC-FDMA.

In case of using the repetition coding, in general, the same data signalis repeated, so the PAPR is increased. In this case, however, if theoriginal data and the duplicate data are repeatedly coded bydifferentiating their size or phase, undergo DFT (Discrete FourierTransform) or IDFT (Inverse Discrete Fourier Transform) and IFFT(Inverse Fast Fourier Transform) (in the form of SC FDMA), and aretransmitted, a gain in terms of PAPR can be obtained.

In the SC-FDMA scheme, the subcarrier allocating unit 130 may performDFT on the contiguous subcarrier, a frequency band used for transmittingthe original data or the duplicate data. The data, which has undergonethe DFT process with respect to the contiguous subcarrier on a singleOFDM symbol, is converted into a signal of frequency domain. Thesubcarrier allocating unit 130 performs IFFT on the signal which hasundergone the DFT process over the entire frequency band to convert itinto a signal of a time domain.

In case of using the OFDMA scheme, unlike the SC-FDMA scheme, thetransmitter can immediately perform IFFT on the subcarrier withoutperforming DFT process to convert it into a signal of a time domain. Inthis manner, each OFDM symbol may undergo DFT spreading and then IFFT tomaintain low PAPR characteristics.

An example of a simple method for differentiating the size or the phasemay be an application of unitary matrix to original data. Namely,N-dimension unitary matrix may be multiplied to the original data toobtain one original data and the (N−1) number of duplicate data.

Equation 1 shows an example of the method of generating duplicate databy using the unitary matrix. The matrix ‘C’ is a unitary matrix.

MathFigure 1

$\begin{matrix}{C = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & j & {- 1} & {- j} \\1 & {- 1} & 1 & {- 1} \\1 & {- j} & {- 1} & j\end{bmatrix}} & \lbrack {{Math}.\mspace{14mu} 1} \rbrack\end{matrix}$

For one example, if four original data to which the matrix ‘C’ isapplied is S₀,S₁,S₂,S₃, one duplicate data S₀,S₁,S₂,S₃, which is thesame as the original data, is generated by a first row 1,1,1,1, and theother three remaining duplicate data are S₀,jS₁,−S₂,−jS₃,S₀,−S₁, S₂,−S₃,and S₀,−jS₁,−S₂,jS₃, respectively.

For another example of a simple method of differentiating the size orthe phase, a Zadoff-Chu (ZC) CAZAC (Constant Amplitude ZeroAuto-Correlation) sequence may be applied. As for the ZC CAZAC sequence,one of CAZAC sequences, if ‘N’ is the length of a CAZAC sequence, apositive integer, and an index ‘M’ is a prime number (‘M’ is a naturalnumber of ‘N’ or smaller, and ‘M’ and ‘N’ are prime numbers with eachother) relatively compared with ‘N’, the kth element of the Mth CAZACsequence may be expressed by equation 2 shown below:

MathFigure 2

$\begin{matrix}{{{c( {{k;N},M} )} = {\exp\{ {- \frac{j\;\pi\;{{Mk}( {k + 1} )}}{N}} \}}}{{where}\mspace{14mu} N\mspace{14mu}{is}\mspace{14mu}{an}\mspace{14mu}{odd}\mspace{14mu}{vmber}}{{c( {{k;N},M} )} = {\exp\{ {- \frac{j\;\pi\;{Mk}^{2}}{N}} \}}}{{where}\mspace{14mu} N\mspace{14mu}{is}\mspace{14mu}{an}\mspace{14mu}{odd}\mspace{14mu}{vmber}}} & \lbrack {{Math}.\mspace{14mu} 2} \rbrack\end{matrix}$

This is merely an example, and any other sequences having goodcorrelation characteristics may be applied. For different terminals,channels may be discriminated by applying ZC CAZAC sequences each havinga different circular shift value.

The unitary matrix ‘C’ or the CAZAC sequence used for generating theduplicate data by changing the size or the phase of the original data asdescribed above is merely an example. Namely, the unitary matrix usedfor generating the duplicate data may be a 3×3 matrix, a 5×5 matrix, orthe like, besides 4×4 matrix. Also, the size ‘k’ may be 2, 3, or else,not necessarily ‘1’, and any matrixes may be used so long as they canmaintain orthogonality between duplicate data.

The method of repetition coding will be described in detail. In order toclarify the description, if repetition is ‘2’, the size of k=1 will betaken as an example.

FIG. 4 shows a method of repetition coding according to anotherembodiment of the present invention.

With reference to FIG. 4, the repetition coding method includesrepeating information bits in units of small data. Namely, according tothis repetition coding method, the results of repetition coding havesuch a form that duplicate data is distributively disposed betweenoriginal data in view of radio resource domain (time domain or frequencydomain). Accordingly, one duplicate data is added per original data,like S₀,α₀S₀,S₁,α₁S₁,S₂,α₂S₂, . . . , S_(N),α_(N)S_(N). Here, the phasedifference θ between the original data and the duplicate data may bevariably set to 0, π/2, π/4, π/6, etc., besides π.

FIG. 5 shows a method of repetition coding according to an embodiment ofthe present invention.

With reference to FIG. 5, the repetition coding method includesrepeating information bits in units of burst. Namely, according to thismethod, the results of repetition coding have such a form that originaldata and duplicate data are locally gather together, in view of radioresource domain (time domain or frequency domain). Accordingly, a set ofduplicate data is added to the end of a set of original data, like S₀,S₁, S₂, . . . , S_(N),α₀S₀,α₁S₁,α₂S₂, . . . , α_(N)S_(N). Here, thephase difference θ between the original data and the duplicate data maybe variably set to 0, π/2, π/4, π/6, etc., besides π.

The method of repetition coding may be performed variably in addition tothose methods as shown in FIGS. 4 and 5.

A method of allocating original data and duplicate data to eachsubcarrier will now be described. Radio resources may be allocated tothe original data and the duplicate data generated according to themethod of FIG. 4 or the method of FIG. 5 by using one of a time axis anda frequency axis as a preferential reference. Here, it is assumed thatthe size (k) of the duplicate data is 1.

Table 1 shows the case of the repetition coding as shown in FIG. 4, inwhich when α₀=α₁= . . . =α_(N)=−1 (namely, when the phase difference θis π), the original data and the duplicate data are distributivelydisposed in the physical radio resource domain (time domain or frequencydomain) and subcarriers are allocated. Namely, the results of therepetition coding are S₀,−S₀,S₁,−S₁,S₂,−S₂, . . . , S_(N),−S_(N).

TABLE 1 OFDM symbol index subcarrier index #1 #2 . . . #1 S₀ S₁ . . . #2−S₀ −S₁ . . . #3 S₁₀ S₁₁ . . . #4 −S₁₀ −S₁₁ . . . #5 S₂₀ S₂₁ . . . #6−S₂₀ −S₂₁ . . . #7 S₃₀ S₃₁ . . . #8 −S₃₀ −S₃₁ . . . . . . . . . . . .

With reference to Table 1, S₀ and −S₀ are mapped to subcarriers #1 and#2 on an OFDM symbol #1. S₁ and −S₁ are mapped to subcarriers #1 and #2on an OFDM symbol #2. In the same manner, S₉ and −S₉ are mapped tosubcarriers #1 and #2 on an OFDM symbol #9. In the same manner, S₁₀ and−S₁₀ are mapped to subcarriers #3 and #4 on an OFDM symbol #1. Theoriginal data and the duplicate data are mapped to the respectivesubcarriers on the other remaining OFDM symbols in the same manner.

Table 2 shows the case of the repetition coding as shown in FIG. 5, inwhich when α₀=α₁= . . . =α_(N)=−1 (namely, when the phase difference θis π), original data and duplicate data are locally gather together inthe physical radio resource domain (time domain or frequency domain) andsubcarriers are allocated. Namely, the results of the repetition codingare S₀,S₁,S₂, . . . , S_(N),−S₀,−S₁,−S₂, . . . , −S_(N).

TABLE 2 OFDM symbol index subcarrier index #1 #2 . . . #1 S₀ S₁ . . . #2S₁₀ S₁₁ . . . #3 S₂₀ S₂₁ . . . . . . . . . . . . . . . #k −S₀ −S₁ . . .#k + 1 −S₁₀ −S₁₁ . . . #k + 2 −S₂₀ −S₂₁ . . . . . . . . . . . . . . .

When information bits are repeatedly coded in units of burst data, radioresources are allocated such that duplicate data is allocated startingfrom a position where allocation of original data is finished.

With reference to Table 2, with respect to the original data, OFDMsymbols #1 to #9 are first allocated in the subcarrier #1, and the OFDMsymbols #1 to #9 are then allocated in the subcarrier #2. Resourceallocation for the duplicate data starts from a position where resourceallocation for the original data is finished. With respect to theduplicate data, the OFDM symbols #1 to #9 are first allocated in thesubcarrier #k, and the OFDM symbols #1 to #9 are then allocated in thesubcarrier #k+1.

Table 3 shows the case of repetition coding as shown in FIG. 4, in whichwhen α₀=α₁= . . . =α_(N)=1 (namely, when the phase difference θ is 0),the original data and the duplicate data are distributively disposed inthe physical radio resource domain (time domain or frequency domain) andsubcarriers are allocated. Namely, the results of the repetition codingare S₀,S₀,S₁,S₁,S₂,S₂, . . . , S_(N),S_(N).

TABLE 3 OFDM symbol index subcarrier index #1 #2 . . . #1 S₀ S₁ . . . #2S₀ S₁ . . . #3 S₁₀ S₁₁ . . . #4 S₁₀ S₁₁ . . . #5 S₂₀ S₂₁ . . . #6 S₂₀S₂₁ . . . #7 S₃₀ S₃₁ . . . #8 S₃₀ S₃₁ . . . . . . . . . . . .

With reference to Table 3, unlike the case of Table 1, the phasedifference θ is 0, a signal has original data and duplicate data whichhave the same phase. The order of resource allocation is the same asthat of Table 1.

Table 4 shows the case of repetition coding as shown in FIG. 5, in whichin which when α₀=α₁= . . . =α_(N)=−1 (namely, when the phase differenceθ is 0), original data and duplicate data are locally gather together inthe physical radio resource domain (time domain or frequency domain) andsubcarriers are allocated. Namely, the results of the repetition codingare S₀,S₁,S₂, . . . , S_(N),S₀,S₁,S₂, . . . , S_(N).

TABLE 4 OFDM symbol index subcarrier index #1 #2 . . . #1 S₀ S₁ . . . #2S₁₀ S₁₁ . . . #3 S₂₀ S₂₁ . . . . . . . . . . . . . . . #k S₀ S₁ . . .#k + 1 S₁₀ S₁₁ . . . #k + 2 S₂₀ S₂₁ . . . . . . . . . . . . . . .

With reference to Table 4, unlike the case of Table 2, the phasedifference is 0, and a signal has original data and duplicate data whichhave the same phase. The order or resource allocation is the same asthat of Table 2.

FIG. 6 is a graph comparatively showing PAPRs in case of using therepetition coding according to Table 1 to Table 4, in which a horizontalaxis indicates the size of PAPRs in SC-FDMA (Single Carrier-FDMA)employing 24 DFT (Discrete Fourier Transform) by decibel (dB), and avertical axis indicates a CDF (Cumulative Distribution Function)capacity of PAPRs. For comparison, a PAPR in the general OFDMA is alsoshown.

With reference to FIG. 6, (1) shows the case of Table 1, (2) shows thecase of Table 2, (3) shows the case of Table 3, (4) shows the case ofTable 4, and (5) shows the case of using the related art repetitioncoding technique.

As shown in the graph, it is noted that the case (1) has a remarkablylow PAPR, and the cases (1) to (4) have lower PAPRs than that of thecase (5). Namely, by discriminating the original data and the duplicatedata, the results of the repetition coding, mapping the duplicate datato a modulation symbol having a different phase from that of theoriginal data, and transmitting data, the PAPR can be lowered unlike thecase of the general repetition coding.

All functions described above may be performed by a processor such as amicroprocessor, a controller, a microcontroller, and an applicationspecific integrated circuit (ASIC) according to software or program codefor performing the functions. The program code may be designed,developed, and implemented on the basis of the descriptions of thepresent invention, and this is well known to those skilled in the art.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

The invention claimed is:
 1. A method of transmitting data in a wirelesscommunication system, the method comprising: generating duplicate databy using repetition coding, the duplicate data being the same asoriginal data; changing the phase of the duplicate data; allocating theoriginal data and the phase-changed duplicate data to the subcarriers ina same orthogonal frequency division multiplexing (OFDM) symbol; andtransmitting the original data and the phase-changed duplicate data,wherein the original data are transmitted through a first frequency bandbeing comprised of contiguous subcarriers and the phase-changedduplicate data are transmitted through a second frequency band beingcomprised of contiguous subcarriers, the first frequency band and thesecond frequency band are different frequency bands in frequency domain.2. The method of claim 1, wherein the phase of the duplicate data arechanged by a unitary matrix ‘C’ which is $C = {\begin{bmatrix}1 & 1 & 1 & 1 \\1 & j & {- 1} & {- j} \\1 & {- 1} & 1 & {- 1} \\1 & {- j} & {- 1} & j\end{bmatrix}.}$
 3. The method of claim 1, wherein the phase of theduplicate data are changed by a CAZAC (Constant Amplitude ZeroAuto-Correlation) sequence.
 4. A method of transmitting data in awireless communication system, the method comprising: generatingduplicate data which is the same as original data by using repetitioncoding; changing the size and the phase of the duplicate data;allocating the original data and the duplicate data with the changedsize and phase to the subcarriers in a same orthogonal frequencydivision multiplexing (OFDM) symbol; and transmitting the original dataand the duplicate data with the changed size and phase.
 5. The method ofclaim 4, further comprising: after the size and the phase of theduplicate data are changed, performing discrete fourier transform (DFT)and inverse fast fourier transform (IFFT) in sequence.
 6. A datatransmitter comprising: a data processing unit to perform repetitioncoding for original data to generate duplicate data; a data changingunit to change the phase of the duplicate data; and a subcarrierallocating unit to map the original data and the phase-changed duplicatedata to subcarriers in a same orthogonal frequency division multiplexing(OFDM) symbol, wherein the original data are transmitted through a firstfrequency band being comprised of contiguous subcarriers and thephase-changed duplicate data are transmitted through a second frequencyband being comprised of contiguous subcarriers, the first frequency bandand the second frequency band are different frequency bands in frequencydomain.
 7. A method of transmitting data in a wireless communicationsystem, the method comprising: generating second data from first data byusing a coding scheme, the second data taken from the first data,wherein the coding scheme is used to distribute the second data besidethe first data and to change a phase of the second data; transmittingthe first data and the second data, wherein the second data is allocatedafter the first data, wherein the first data is transmitted throughfirst frequency values being comprised of contiguous subcarriers and thesecond data is transmitted through second frequency values beingcomprised of contiguous subcarriers, wherein the first frequency valuesand the second frequency values are different in a frequency domain. 8.The method of claim 7, wherein a phase difference between the first dataand the second data is one of 0, π/2, π/4 and π/6.
 9. The method ofclaim 7, wherein the second data is generated based on a Cazac sequence.10. The method of claim 7, the method further includes: modulating thefirst data and the second data.
 11. An apparatus of transmitting data ina wireless communication system, the apparatus comprising: a dataprocessor for generating second data from first data by using a codingscheme, the second data taken from the first data, wherein the codingscheme is used to distribute the second data beside the first data andto change a phase of the second data, a transmitter for transmitting thefirst data and the second data, wherein the second data is allocatedafter a part of the first data, wherein the first data is transmittedthrough first frequency values being comprised of contiguous subcarriersand the second data is transmitted through second frequency values beingcomprised of contiguous subcarriers, wherein the first frequency valuesand the second frequency values are different in a frequency domain. 12.The apparatus of claim 11, wherein a phase difference between the firstdata and the second data is one of 0, π/2, π/4 and π/6.
 13. Theapparatus of claim 11, wherein the second data is generated based on aCazac sequence.
 14. The apparatus of claim 11, the apparatus furtherincludes: a modulator to modulate the first data and the second data.